Automatic pressing tool for anisotropic permanent magnets

ABSTRACT

AN AUTOMATIC PRESS FOR MAKING PERMANENT MAGNETS FROM MAGNET POWDER WHEREIN A MOLD HAS AN OPENING FOR RECEIVING THE MAGNET POWDER, A PRESS RAM FOR PRESSING THE MAGNET POWDER AND AN ELECTROMAGNET MEANS FOR ESTABLISHING A MAGNETIC FIELD WHILE THE MAGNET POWDER IS BEING PRESSED; THE MAGNET POWDER IS FED INTO THE MOLD   OPENING BY MEANS OF A FILLING DEVICE CARRYING A QUANTITY OF THE MAGNET POWDER, AND A DEMAGNETIZING COIL OPERATIVELY CONNECTED TO THE FILLING DEVICE DEMAGNETIZES THE ADJACENT PARTS OF THE PRESSING TOOL AFTER EACH STOCK OF THE RAM.

Feb. 23, 1971 E. STEINGROEVER AUTOMATIC PRESSING TOOL FOR AN'I SOTROPICPERMANENT MAGNETS Filed Jan. 21, 1969 Z V 55 W W United States Patent3,564,654 AUTOMATIC PRESSING TOOL FOR ANISOTROPIC PERMANENT MAGNETSErich Steingroever, Bonn, Germany, assignor to Magnetfabrik Bonn GmbHvorm. Gewerkschaft, Bonn, Germany, a corporation of Germany Filed Jan.21, 1969, Ser. No. 792,291 Claims priority, application Germany, Mar.19, 1968, P 16 08 355.9 Int. Cl. B30b 11/02, 15/30 US. Cl. 18-165 ClaimsABSTRACT OF THE DISCLOSURE BACKGROUND OF THE INVENTION The inventionconcerns an automatic pressing tool for anisotropic permanent magnetswhich are produced from a magnet powder which may also include a binder.

In the case of such pressing tools, the prior art arrangements havecaused great difficulties with respect to filling the press holerepeatedly with equal quantities of magnet powder. During use of suchprior art devices, the parts of the pressing tool surrounding the presshole are magnetized through the magnetic field applied during pressing,causing magnetic poles to develop at the edges; a certain amount ofmagnet powder will adhere to these edges, forming at times a bridgeacross the press hole and preventing the equal flowing-in of the magnetpowder into the press hole. This phenomenon occurs particularly in thecase of pressing tools for thin-walled elements.

SUMMARY OF THE INVENTION It is, therefore, an object of the presentinvention to solve the problem associated with prior art devices.

Another object of this invention is to provide an automatic pressingtool with a faultless operation by demagnetization of the pressing tool.

This invention has another object in that a demagnetizing coil isattached to the filling device for an automatic pressing tool forunitary movement and energization with the filling device.

The present invention is summarized in an automatic press for makinpermanent magnets from magnet powder wherein a magnet-forming mold hasaperture means for receiving the magnet powder, ram means for pressingthe magnet powder, electromagnetic means associated with the mold andestablishing a magnetic field in which the magnet powder is pressed, afilling device carrying the magnet powder is transversely movable forfilling the aperture means, and demagnetizin means is carried by thefilling means to cause demagnetization of the adjacent parts of theautomatic press.

Other objects and advantages of the present invention will becomeapparent from the following description taken in conjunction with theaccompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a cross section of anautomatic press em- 3,564,654 Patented Feb. 23, 1971 bodying the presentinvention and with the press rams being partially shown; and

FIG. 2 is a top plan view of FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENT As is illustrated in FIG. 1, thepresent invention is embodied in an automatic press, parts of which havebeen omitted for the sake of brevity. The automatic press includes abase plate 1 having a pressing matrix 2 in the form of an annulus orsleeve. The inner surface of the matrix 2 defines the outer wall of acircular aperture 5, the inner wall of which is defined by a fixedmiddle ram 3; the lower wall of the press hole 5 is defined by the uppersurface of a lower press ram 4 which is movable up and down as viewed inFIG, 1. After being filled with magnet powder the press hole 5 issubject to a radial magnetic field created by means of the field coil 6,which magnetic field has a magnetic flux as generally shown in thebroken lines of FIG. 1. The magnetic flux is shown as passing throughthe fixed middle ram 3, the press hole 5, the matrix 2, the base plate 1and through the ground pot 7 made of soft iron. The pressing process iscarried out by means of the upper ram 8 which has the same cylindricalconfiguration as the press hole 5 and is movable up and down as viewedin FIG. 1. After the pressing process, the pressed article in the formof a permanent magnet annulus is ejected from the base plate 1 by meansof the upward movement of the lower ram 4 which reciprocates back to itsoriginal position so that the press hole 5 will again be free.

The filling device 9 is slidably mounted on the top of the base plate 1and reciprocates from the right as viewed in FIG. 1. A seal 10 isdisposed adjacent the outlet of the filling device 9 and is inengagement with the top surface of the base plate 1 so that the loosemagnetic powder 11 is retained in the filling device until it is alignedwith the press hole 5. The trailing edge of the filling device 9 issecured to a reciprocatin shaft which affects a reciprocant movement ofthe filling device by any suitable power means (not shown). The frontportion of the filling device carries a demagnetizing coil 12 having acore 13 made of laminated iron. A buffer strip 14 made of felt or spongerubber is attached to the forward portion of the demagnetizin coil 12 todefine the leading edge of the filling device 9 and to push an ejectedmolded article to the left as viewed in FIG. 1.

During the normal sequence of operation of the automatic pressing tool,a switch (not shown) energizes the demagnetizing coil 12 in response toinitial movement of the filling device 9 to the left as viewed inFIG. 1. During its leftward movement, the adjacent portions of the baseplate 1 surrounding the pressing hole 5 are subject to an alternatingmagnetic field of at first rising then declining strength and as aresult will be completely demagnetized. As is illustrated in FIG. 2, thefilling device 9 traverses the base plate 1 to an extreme position asindicated by the dashed lines for the buffer strip 14. During suchleftward movement, the press hole 5 is completely filled with the magnetpowder 11 which is permitted to drop freely into such hole and fill itevenly. The filling device 9 is thereafter returned to its originalposition as shown in FIG. 1 after which the upper ram 8 moves downwardlyto compress the powder into press hole 5. During such downward movement,the electromagnetic coil 6 is energized by a suitable switch (not shown)creating the radial magnetic field which affects alignment of theparticles in the magnetic powder as it is being pressed by the upper ram8.

After the permanent magnet it formed, the ram 8 is retracted upwardlyand the lower ram 4 moves upwardly (as is viewed in FIG. 1) to alfectthe'permanent magnet from the matrix 2. The above arrangement has theparticular advantage in that the demagnetizing device does not have tobe changed during the replacement of different pressing matrixes in theprimary mold. Accordingly, all parts of the pressing tool aredemagnetized, which are transversed by the iron coil 13 during themovement of the filling device 9.

Inasmuch as the present invention is subject to many variations,modifications and changes in detail, it is intended that all mattercontained in the foregoing description or shown in the accompanyingdrawin shall be interpreted as illustrative and not in a limitin sense.

What is claimed is:

1. In an automatic press for making permanent magnets from magnetpowder, the combination comprising a magnet-forming mold having aperturemeans for receiving magnet powder,

ram means for pressing the magnet powder,

electromagnetic means associated with said mold and establishing amagnetic field in which the magnet powder is pressed,

filling means transversely movable to said aperture means and carrying aquantity of magnet powder for supplying said aperture means, anddemagnetizing means carried by said filling means and demagnetizingadjacent parts of the automatic press.

2. The invention as recited in claim 1 wherein said demagnetizing meanscomprises an A.C. coil energized 4 in response to transverse movement ofsaid filling means.

3. The invention as recited in claim 2 wherein said A.C. coil is mountedon a front portion of said filling means.

4. The invention as recited in claim 3 wherein said filling meansincludes an opening for supplying magnet powder to said aperture meansand a seal for said opening engaging a surface of said mold.

5. The invention as recited in claim 4 wherein said filling mearisincludes a buflFer strip on its leading edge to remove articles ejectedfrom said aperture means.

References Cited UNITED STATES PATENTS 2,641,820 6/1953 Rivers 251032,842,827 7/1958 Nickelson 25103 3,189,667 6/1965 Buttner et al.18magnet dig. 3,213,511 10/1965 Petruggi 25103X 3,232,987 2/1966 Baxter18magnet dig. 3,387,066 6/1968 Martin et a1. 18magnet dig. 3,397,4358/1968 Jelesiewicz 25-103 3,416,191 12/1968 Richter et al. 1816.5'

I. HOWARD FLINT, J R, Primary Examiner US. Cl. X.R.

1816, 5, magnet dig; 264-24

